Terowongan

1. Surveillance and Control Systems for Highway Tunnels
Unlike open highways, tunnels require special attention to maintain safety under normal and
abnormal traffic conditions. Most modern tunnels, including their approach roads, require a
centralized control system to meet these goals Al though not all tunnels require the same
attention or installed features, they all have the following general features. Note:
The dimensions shown in this chapter are indicative guidelines. All English unit equivalents
are soft.(rounded) conversions of metric.]
SURVEILLANCE AND CONTROL SYSTEMS
These systems provide means to
1. Monitor traffic flow and identi& impending congestion or stoppages caused by
breakdowns or accidents
2. Maintain a safe tunnel environment, responsive to traffic density and travel speed
3. Communicate travel restrictions to motorists approaching and passing through the tunnel
4. Mobilize emergency response to clear mcidcnts within the
5. Initiate, when appropriate, the necessary systems operation for emergency conditions
6. Monitor the status of tunnel service equipment to ensure continued operation and
availability when needed.
Central Control
The contml center is usually located in a tunnel ventilation or administration building and is
manned 24 hours a day. For low-volume rural tunnels or short-length tunnels that are really
extended underpasses, an alternative is part- time remote monitoring with tunnel equipment
operating automatically.
Human Control
The common control element is the need for human intervention to judge the extent and
se4verity of incidents, followed by initiation and supervision of corrective measures and
emergency response until conditions have returned to normal.

2. OVERVIEW OF AVAILABLE TECHNOLOGY
Tunnel Configuration
Most mad tunnels are dual-bored or immersed tubes each carrying two or three full-width
traffic lanes with an offset or minishoulder on both sides to safety barriers (see Figure 24-1).
Approach roadway shoulders are carried through short tunnels but are eliiiiinatéd or reduced
to offsets on high-construction-cost tunnels. A rule of thumb states the cost of tunnel
cónstniction will directly increase on an algorithmic scale with the tunnel diameter. Full-time
traffic monitoring has been shown to be more cost effective than providing full shoulders.
Thnnels are nornially designed for directional operation with provisions to operate btdirection
ally should the adjaceni boreltuhe be closed for emergencies maintenance. Crosspassages
between the tunnels are provided for emergency evacuation, access to fight tunnel fires, a
location to install equipment control centers, and in a number of long tunnels, vehicle
turnaround.
Tunnel Surveillance and Control
Equipment
The following traffic control devices, used to monitor vehicle flow, stop traffic, close
individual lanes and/or a binnel, and provide visual instructions to motorists passing through
the tunnel, are installed in the tunnel roadway on the walls or suspended from the ceiling.
Fig. 24-1. Typical tunnel cross section.

3.  Vehicle detectors Loop detectors embedded in ech traffic lane with video radar/microwave
detectors mounted overhead to support or replace the loop detectors are used to monitor
vehicle volume, speed, and occupancy and, by processing this data, identify the
probability of stoppages.
 Signs and signals. Spaced at regular intervals over the roadway are 10- or 12-character
variable-message sighs (VMS) with lane-use signals at both ends. The signs are spaced at
regular intervals so that two units are visible ahead. Below the VMS and mounted
horizontally is.a standard three-head: traffic signal. These units should be double-faced to
provide a front to back display when the tunnel is operating reversed or bidirectional. This
combination of sign and signals provides traffic control continuously through the tunnel
(áee Figure 24-2) Alternatives to this arrangement, particularly where space is at a
premium are - -
— The VMS sign centered between a dual-purpose lane-usel tiaf tic signal units - r
— Interval location of.VMS/signals/VMS/etc.
— Smaller (vertical) units at closer spacing
• TekvLcion cameras. Closed-circuit television (CCIV) cameras, either ceiling- or wall-
mounted, are spaced throughout the tunnel to provide full coverage. They are coupled with
the vehicle detector to provide the visual verification that an mcident has occurred.
• Emergency exits. The locations of cross--passage doàrs are marked with strobe lights
mounted above or at walking level together with a flashing arrow and the word exit
included on the wall side of the overhead sign and signal dispJays.
Safety and Environmental MotiltoHng
The following monitors are used to detect fires, measure air pollution levels, and sense
dangerous spills in the tunnel:
• Heat detectors. Ceiling-mounted thermal- detectors or infared area -detectors provided
as a backup alert in support of the CCTV system to detent a fire. See Chapter 19 for
an in- depth discussion of detectors.

4. Fig. 24-2: Tunnel variable-message sign at cross-passageway
• Carbon monoxide monitors. Tunnel air is samplediso units such as infrared absorption
analyzers can measure carbon monoxide (CO) levels. lmprovepents allow monitoring
of NO1 to be coupled to CO monitoring. Readings from these sensors can be used for
ventilation control (see Chapt& 20).
• Visibility monitoring. Reductions of visual range in the tunnel aie measured with a
wall-mounted light transmitter and receiver that record the degree of obscurity caused
by patti- des and diesel smoke. In tunnels with a high percentage of diesel-powered
vehicles, ventilation is more often controlled by visibility requirements than CO.
• Air velocity monitors. Anemometers or ultrasonic transducers are mounted above the
traffic stream to measure tunnel air velocity and direction of flow. This data is fed into
the ventilation control system.
• Hydrocarbon monitors. Gas sensors in the tunnel drainage system detect quantities of
potentially explosive and/or hazanions materials. See Chapter 23.
Voice Communication. A combination of radio and telephones is used to communicate
directly with motorists through their car radios and maintain communication between tunnel
and emergency response personnel within the tunnels and to units outside the tunnel. These
systems and their role in fire safety are addressed in Chapter 19. They include
• Tetephone& Throughout the tunnels and ventllation buildings, there is a telephone system
built around an electronic private automatic branch exchange (EPABX) for internal and
external calling.
• QEJ1 boxes. Motorist and call boxes are located in the cross- passages to provide direct
contact with the tunnel operator.
Facility radio. Operations and maintenance personnel use a two-way FM arid/or VHF radio
system for communication between the control center, vehicles with mobile units, and
personnel using handheld rransceivers.

5. • Miscellaneous radio. Separate radio systems and/or additional channels linked with the
facility radio are provided for
police, fire department, and emergency medical response.
• AM/FM radio rebroadcast. The rebroadcast system provides continuous broadcast band
reception for the motorist while passing through the tunnel. With this system the operator can
interrupt commercial broadcasts to relay information directly to the motorists over their car
radios.
Approach Koad Configuration
A plaza immediately in front of the tunnel portal or between the approach roads is used to
transfer traffic from one roadway to the other, for bidirectional tunnel operations, to turn back
oversize and hazardous materials carriers, and to provide access to the portal buildings. A
typical arrangement
the plaza including the location and type of traffic control devices is shown in Figure 24-3.
Oversize Vehicles. The identification, stopping, and diverting of oversize and overheight
vehicles requires a five- station layout that will extend one or mote miles before the tunnel
plaza and tunnel portal. The location of these installations is centered around station No. 4,
the last exit road before the tunnel. If there is a long gap from the last exit to the tunnel, the
crossover plaza is then used to turn back vehicles. The linear arrangement of these
installations are
1. Overheight Detector. Detection is made using an infrared light beam projected across the
roadway just below clearance height (5 rn/I 2.5 It) with a transmitter on one side and a
receiver on the other. When the beam is broken, a signal is sent to stations 2 and 3. The
distance between stations 1 and 2 should be sufficient to trigger No. 2 flashing lights and gain
driver recognition (5-sec minimum, or 135 rn [440 ft] at 100 kph [60 mph]).
2. Flashing Overheight Sign. Overheight detector signal activates two wig-wig flashing lights
on a fixed panel sign that is downstream with the message, “When Flashing All Trucks Exit
to Inspection Station Ahead.” The flashing time is usually set for 15 sec and may catch
several trucks.
3. Inspection Station. The inspection station is configured similar to a weighting station. The
No. I detector alarm alerts the station staff to be prepared to sort out the errant vehicle and
direct it to the exit (see No. 4) or turn it back.
4. Last Roadway Exit. Jt is unlikely that once told to leave the roadway at the next exit the
driver will continue and enter the tunnel; however, if this does happen or the driver does not
stop at the inspection station, the vehicle will be detected again at the next checkpoint (No.
5).
5. Fail-Safe Overheight Detector. The fail-safe detector is similar to the first detector, but
when triggered all signs and

6. -signals ahead leading into the tunnel are turned to stop/red, thus bringing the total traffic
stream to a halt and preventing the errant truck from entering the tunneL The police or tunnel
staff will then sort out the traffic jam and aporehend the violator. The linear arrangement of
the above installation in urban settings may be severely truncated or replaced by an overpass
structure with minimum clearance immediately before the tunnel portal.
Fig. 24-3. Tunnel portal plaza.
In urban tunnels, where detection and stopping over- height vehicles occurs in a plaza
immediately before the portal, a crash curtain consisting of weighted-blocks chain suspended
at clearance height acràss the detector location gives a sound/impact alert to the driver.
Hazardous Materials. Some classes of materials—explosive, toxic, and poisonous—are
prohibited passage in tunnels. There are circumstances, however, where flamma
ble and other hazardous materials are allowed passage because alternative routes are long or
will pass through local streets, which is considered more of a hazard. To allow for this
passnge, vehicles are directed to -a -holding area as shown on Figure 24-3 and at scheduled
times are escorted through the tunnel -
Approach Road Traffic Con troL The combination of fixed panel signs, variable-message
signs, and traffic and lane signals is used to familiarize motorists with the sign and signal
arrangements they will see in the tunnel. These control devices will be used to stop and
maneuver traffic to single lanes or direct traffic to cross over to the other tunnel.
Approach rood signs and signals. The overhead signs and signals are larger than the tunnel
units so as to be visible from a greater distance and attract the attention needed Normally,
three sets of sign/signal units are needed to advise action ahead, initiate this action, and
confirm -the travel restriction (see Figure 244). The traffic signals should be paired with the
signing to replicate standard intersection arrangements.
Approach road CCIV. The outdoor cameras are fined with a remotely controlled mechanism
to pan and tilt the camera and zoom the lens for area scanning and close-up viewing. A
minimum of two cameras, one looking into the portal and the other looking away from the
portal down the approach road, is required to supplement the series of in-tunnel cameras and
view the approach road (see Figure 24-5).
TRAffIC CONTROL CONCEPTS
Modes of Operation

7. The tunnel arid approach roads should be equipped to make all changes in traffic operation
using the sign and signal units described previously. As there is usually no time to call for
police or tunnel staff to manually assist in traffic control for accidents, the control devices
and their use must
10 CHARACTERS
LANE USAGE SIGN ir TFtAFFIC SIGNALS’
MESSAGES:
NO ENTRY • LEFT LANE CLOSED • CAUTiON FOG
NO PASSING — GO STOP AHEAD
STOP HERE .- STOP GO • MERGC—---->
RIGHT LANE • CAUTION ICE AHEAD • <--—MERGE
CLOSED • FLASHING OR MOVING CHEVRON

8. Fig. 24-4. Approach road signing..
be foolproof and easy to understand. Traffic changes fall into two major categories:
scheduled changes and incident response. The former is a timed action with manual support
staffing out on the approach road. Incident response is a yeaction requiring quick sign/signal
response at the incident site and tunnel portal and then travel back to intercept approaching
traffic to close lanes or redirect tunnel entry. Far
Fig. 24—S. ca-V camera arrangement.
incident response, the first objective is to stop entry of traffic into the tunnel. The holding
point is the approaãh crossover (see Figure 24-3). Inside the tunnel there are always some

9. motorists trapped behind the incident, thus creating a need for dual response to deal with the
stopped vehicles and to clear the traffic stream behind.
Sign/Signal Displays
The operator’s tools to orchestrate operations are packaged sign/signal displays, known as
sign/signal plans, resident in his computer. The plans, using messages shown in Figure 24-4
with associated signals, can be prepared using the following operating procedures to organize
the displays.
Basic Signing Plans
Five basic sign/signal plans (displays) are needed to control traffic, with several supplemental
plans to modify these five basic plans. The following two-letter designations used to develop
sign/signal plans are shown for a typical two-lane bidirectional tunnel port of a dual two-lane
facility.
• NN—Both lanes operating in the normal mode at posted
• NC or CN—One lane open, the other closed. This plan is used for scheduled closure of one
lane, left or tight, with the adjacent lane operating normally at reduced speed.
• CC—Both lanes closed. This plan is used to clear the tunnel for maintenance with the
adjacent tunnel in two-way operation. Two or more steps are needed to reach the final closure
state.
• NE or EN—One lane open, one closed. This plan is used for response to a minor incident in
which traffic is allowed to continue flow past the incident, or the first stage of a tunnel
closure to allow trapped vehicles to exit the tunnel.
• EE—Major incident plan. ‘Ibis plan, like the minor incident
plan, reacts from the incident site closing the tunnel upstream
while the lanes downstream remain open to allow traffic to
clear.
All signing/signal plans must include transition stages from an existing state to any of the
other states or back to normal (NN) (see Figure 24-6).
Condition Change
Most- changes to traffic flow can be accomplished by using a two-step sequence of individual
arid coordinated sigWsignal displays. The initial display should be advisory or warning (e.g.,
Right Lane Closed Ahead), followed by the

10. Fig 24.6. Response plan logic diagram.
action or restriction display (e.g., Keep Left, Right Lane Closed).
Supplemental Plans
These plans call for action by flashing command messages and then returning to the basic
plan. Displays can be flashed on and off or kept in a momentary steady state to stop traffic.
Oration. This plan will alert drivers to reduce speed and set in line the next plan. The plan can
be used as an automatic alert with incident detection to want motorists and give the operator
time to follow with the appropriate action
Speed Change. Reduction in speed on the approach roadways as a result of fog, ice, or snow.
Flow ControL Driving through a tunnel is a traumatic experience for many motorists, causing
overcaution andlor a complete disorientation, and resulting in the need for signing plans to
stabilize traffic flow. A common occurrence in subaqueous tunnels is the loss of speed on the
downgrade caused by overreaction to brake lights. This is followed by a loss of orientation
and failure to accelerate on the upgrade, resulting in a sluggish crawl that greatly reduces
throughput of the tunnel. This condition can only be broken up by platooning traffic to break
the inertia or, in this case, lack of inertia. Plaboning is accomplished by stopping entry at the
tunnel portal much like a signalized intersection; When released, traffic will flow freely
through the tunnel until it reaches the end of the crawl. Traffic should again be stopped one or
more times until smooth flow exists throughout the tunnel length.
Stopping time should be limited to a maximum of 3 nun, which is about the extent of
motorists’ patience. The tunnel signs (Figure 24-2) should also• include messages such as
“Maintain XX kph” or “Upgrade, Accelerate.”

11. Stop. This command is used to momentarily halt traffic approaching the tunnel to allow the
turn back of restricted vehicles or escort of vehicles through the tunnel, or as the initial stage
in estabJishing bidirectional flow in the other tunnel.
Action/Advisory. Action message include “Turn on Radio,”“Evacuate the Thnnel,”“Stay in
Lane,” etc.
Normal Operation
Most urban tunnels have more traffic lanes on the approaches than in the tunnel; thus, the
demand exceeds the tunnel madway capacity. After entering the tunnel, traffic becomes
unstable and slow, which further reduces the flow. The dividing line betw&n free flow and
unstable flow can be related to traffic density. As traffic density increases to the optimal flow
rate (veh/hour), free flow exists. Beyond this point, as the density increases, flow and speed
decrease (see Figure 24-7). A means of gauging these traffic changes is the monitoring of
lane occupancy by providing occupancy readouts per lane in the control center. A green
display for a traffic density of 0—20% indicates uncongestedt flow, a yellow of 20—30%
indicates unstable or impeding congestion, and red for over 30% indicates congestion. Once
notified of unstable flow, the operator has the following options or combinations of options to
use:
Traffic monitoring. Flow control or reducing the number of
approach lanes.
Motorist advisoiy Flash tunnel signs to read “Maintain XX kph,” or prompt the motorist to
regain free flow over the radio rebroadcast
Fig. 24-7. Traffic now diagram.
Incident Response

12. The first alert of a possible incident will be received from the lane sensing of a disruption in
flow (breakdown or acci— dent). (See Figure 24-8.) The alert will automatically switch the
console CCTV monitors to display the incident site. After examining the situation, the
operator can verify the in— cident or reject the alami as a false alarm. Should the opera— tor
not respond or delay his response, the sign/signal program will be triggereth initiating the
Caution Plan and a prompt waiting for further instructions from the operator. The usual
sequence after verification is for the operator to select the appropriate response plan. As the
display changes are sent to the field devices, the feedback status is compared with the phange
command to verify proper execution. While calling up the sign/signal plans the operator will
take the following steps:
• Emergency response. Alert the emergency response crew to the location and extent -of the
inéldent. Select the access mutes -to reach the site eitherby counter flow in the incident tunnel
or through the adjacent tunnel and cross-passages.
• Radio broadcast. Flash tunnel signs to read ‘Turn on Radio” and then begin broadcasting
instructions.
Off-site assistance. Notify-police, fire, and medical assistance with routing instructions to
reach the incident site.
• Equipment operation. Change and activate tunnel service equipment—set -ventilation
mode/levels, pressurize water mains, open drainage holding tasks, -stan standby power
generator.
• Response supervision. Maintain overall control of response activities using CCTV, phones,
and radio.
• Nonnalize. After incidcnt clearance, return traffic control devices and tunnel equipment to
normal operating mode.
Tunnel Evacuation
Some accidents may require evacuation actions prompted by sign displays, radio instruction,
and tunnel staff which direct motorists to leave their vehicles and exit the tunnel through
cross-passage or portal. In a fire emergency, evacu

13. Fig. 24-8. Incident management diagram.
of stranded motorists is critical. Tunnel fires are usually identified by CCTV when viewing
incidents; however, traffic queues can block the view or secondary incidents in the queue
may result in a fire, which establishes the need for backup detectors. Operator action is
essential as motorists may attempt to fight the fire with portable extinguishers available from
tunnel niches or in vehicles. They usually will not flee the area until there is a flare-up and
smoke. When smoke buildup occurs, quick, forceful instructions for direction to flee should
be issued using -the rebroadcast radio, strobe lights, and signs at the cross-passages to prompt
this action.
flELD HARDWARE
Detectors
The efficiency of incident detection -depends on the reliability of the vehicle sensing unit.
Present practice employs
detector loops cut into the approach road and tunnel pavement. Standard traffic controllers
like the 170 with programmable logic and communication medium can be used with several
detector amplifiers to collect and process traffic data. Since most tunnels prohibit lane
changing in the tunnel, the sensing of a stoppage can be accomplished in seconds using
developed algorithms such as the queuing and flow-discontinuity programs commonly known
as the California algorithm. With a 180-rn (400-ft) spacing of detector loops in each lane, the
traffic controller will poll the loop amplifier at 1/60-sec intervals to summate 1-sec
measurements of lane occupancy over the loop. This data is then processed locally or at the
control center to develop 1-mm avenges of lane occupancy that are updated every 20 sec and
fed into the algorithm. The sensitivity parameter built into the program will usually be set to
accept a high (2:1) false alarm rate in order to generate quick alarms. This detection
procedure is very successful when the -traffic flow exceeds 400-600 vph per lane. Detection
is uncertain during periods of low volume and at night when lane changing enforcement is
improbable, or it can occur when a vehicle pulls off onto a partial shoulder offset. A second
algorithm based on vehicle accounting can be used to warn the operator when there appears
to be a stalled vehicle somewhere in the tunnel.

14. Freeway traffic management systems are now using video! radar/microwave detectors to
measure flow as a means to identify congestion and incidents. These units could furnish the
vehicle speed input to the algorithm and eliminate the need for dual occupancy loops.
However, until tested and proven in tunnel use, detector loops are recommended for queuing
and counting detection.
Television Cameras - -
It is important that the tunnel be fully covered by the CCTV system to provide clear images
to the operator. The tunnel cameras are fixed-focus and -mounted on the ceiling
or high on the sidewall to view approaching traffic. Positioning cameras to face oncoming
traffic prevents trucks, buses, etc., blocking the camera sight lines. It is possible to add
remotely controlled pan and tilt mechanisms to provide double camera coverage of an
incident site, but this requires higher tunnel headroom.
Solid State Cameras. The cameras are compact charged- couple devices (CCD) fitted with
12.5-mm (0.5-in.) lenses. They are free from image lag, blurring of images. blooming, image
burn, and damage from direct light. Although each camera with a fixed focal lens can cover
more than a 300-rn (990-fl) length of tunnel, the cross section restraint I knits the effective
range to 200 m (660 ft). Horizontal or vertical changes in alignment may reduce this range
significantly, possibly to 75 m (250 ft).
Camera Spacing. A practical method for spacing the cameras in the tunnel begins with a
camera looking in at the exit portal, then going back against the flow locate a camera at 200
m (660 ft) spacing (see Figure 24-5). Followiu this layout, it is possible to plot the camera
sight lines on the tunnel plan and profile to see if full coverage is available. If not, cameras
are added and spaced at less than 660 ft (200 m) to obtain full coverage. It should be noted
the camera vision cone will not produce wall-to-wall, pavement-to-ceiling coverage
immediately in front of the camera, and thus a 25 m (80 ft) sight overlap between cameras is
needed.
When selecting the remaining components of the CCTV system, a balance and assurance of
quality is needed. The camera should have high resolutioji and b housed in a weatherproof
case. Fiber optic or coaxial cables should be used to transmit the video signals directly back
to the control center. Solid state monitors with high screen resolution are standard for control
room display. Since the CCTV sys tem is so important to operations, its configuration should
use quality components and be simple, easily maintained, and free from unneeded fixtures
such as transmission multiplexing, split-screen monitors, etc.
Outdoor Cameras. The outdoor cameras should be fitted with a remotely controlled
motorized zoom lens (1:10 or 1:16) enclosed in a weatherproof case with window
washeriwiper. The camera is mounted on a pan (350°) and tilt (90°) unit. Two outdoor
cameras are recommended at each portal. One is located over the exit roadway to view the
immediate portal area and normally is set looking into the tunnel to complete the tunnel
coverage. The second camera is mounted high on the portal and will view the approach roads.

15. Additional approach road cameras may be needed if the surveillance length is extensive or
road alignment and terrain obstructs the view. The camera height above the roadway also
determines the distance viewing is effective;
increasing height increases depth of view.
Traffic and lane Signals
The traffic and lane signals each have separate use. They are mounted separately and not
mixed together, so as to
avoid conflict in meaning. The traffic signals are used to stop traffic and should have 200-mm
(8-in.) diameter lenses using standard three-signal heads with fiber optic light source. The
outdoor signals are similar, but should have 300-mm (12-in.) lenses. The lane signal is used
for lane control and is mounted over the centerline of each lane using a 300-rum (12-in.) fiber
optic light point for green arrows, yellow slanted down arrows, and red crosses.
Approach Road and Tunnel Signing
Directional Signing. Directional signing should be avoided if possible at the tunnel entrance,
within the tunnel, and just outside the tunnel exil However, in many urban facilities and
where there are entrance and exit roads in the tunnel, this signing is necessary. Logic shows
that the outdoor signing standards are not suitable nor really necessary in a tunnel. With the
tunnel confinement, it is difficult to see more than 75—150 m (250—500 ft) ahead, and
therefore the signing panel and lettersize can be greatly reduced. A second consideration is
that the motorist has little time to read and comprehend lengthy texts; therefore, the message
must be concise. Using standard 300-mm (12-in.) letter heights for two lines of text arranged
to read left to right will result in a compact 900-mm (36-in.) height sign pane (see Figure 24-
9). If there are several such signs in the tunnel, the ceilr ing height can be set to accommodate
900-mm (36-in:) signs. If there are only a few, all or a portion of the sign height may be fitted
into a ceiling notch. If this type of signing is used extensively within the tunnel, similar
arrIngements with larger lettersshould be used on the approach road to familiarize the
motorist.
Regulatory Signing. Regulatory signing is used on the approach roads and in the tunnels to
support the traffic and lane signals. For example, they are used to warn (“Left Lane Closed”),
to impose restrictions (“Stay in Lane”), to provide motorist advice (“Turn on Radio”), or to
command action (“Evacuate Tunnel”). There are several types of variable- message signing
units (blank-out, rotating drum, fiber optic, or LED matrix). The matrix type can provide
almost limitless numbers of messages and has the capacity to illuminate the letters/symbol
points, which is preferred for use in tunnels and approach roads (see Figure 24-10).

16. Fig. 24.9. Directional signing panels.
Fig. 24-10. Matrix variable-message signs.
Overheight Vehicle. The infrared beam transmitter and receiver may be mounted on an
overhead sign bridge, bridge abutment/pier, or on their own poles. To eliminate false alarms
caused by vehicle aerials or birds flying through the beam, a minimum break time is needed
to trigger an alarm. The beam can also be coupled with detector loops to prove the presence
of a vehicle. For bidirectional roadways where it is not possible to erect poles between
opposing travel lanes, two sets of beams are needed with a breaking logic to. determine the
direction of the vehicle.
Fire Detection and Equipment
The frillowing discussion of fife detection and equipment
relates primarily to surveillance and control aspects. For a
discussion of the fire protection aspects, see Chapters 19,
20, and 23.
The first line of fire and smoke detection should be the CCTV system, but standard detectors
are needed to provide backup and to identify hidden fires. Heat detectors should be. used
throäghout the length of the tunnel, subdivided into alarm zones. The detectors, high-wall- or
ceiling-mounted, can be individual point detectors set at a temperature level and rate of rise,
linear therrno cables, or infrared area scanners.

17. Smoke Detection. Alarms can be generated by the visibility monitors when levels fall below
set levels. These uniti are effective for small fires, which can generate large and dangerous
quantities of smoke. To provide effective sensing, the number of monitors and their spacing
should be increased.
Fire Extinguishers. Small fires can be easily controlled with powder or foam extinguishers,
which most motorists know how to use. Extinguishers should be located in tunnel niches at
each entrance door. A control center alarm should be activated when the extinguisher is
removed from its
holdet
Air Quality Monitors Carbon Monoxide Monitors.
The most effective car-
boa monoxide (CO) monitor in terms of reliability, ability to
produce accurate measurements, and need/ease of maintenance and calibration is the pumped
sample infrared absorption type. Each unit is equipped to handle six to eight sampling ports.
The ideal location for the analyzer unit is at each portal, with sampling ports some 15—30 m
(50—100 ft) inside the tunnel on both tunnel walls. This arrangement will provide dqal
measurements in each tunnel, and the short sample tube lengths will enable minimum time
readings. Other similar installations should be at the mid-tunnel and/or quarter point
locations.
Visibility Monitors The visibility monitor consists of a light transmitter and receiver, usually
mounted on the tunnel walls, to measure the smoke/particle content of the tunnel. The
measurement of obscurity is directly related to the degree of visibility in the tunnel, and when
concentrations reach set values fresh air is supplied to dilute this concentration. These units
should be located in similar positions to the CO monitors, where the expected concentration
is highest and where dual readings can be obtained for comparison.
Air Velocity Monitors. The measurement of air movement in the tunnel—velocity and
direction—is needed for control and/or measurement of the ventilation system efficiency.
This is accomplished by installing, inside each portal of both tunnels, ultrasonic transducers
on the walls to point a signal at approximately 3.65 m (12 ft) above the roadway angled
across the roadway at 45° to the receiver on the opposite wall. The analyzer unit can be
housed together with the CO and visibility units.
Communication Equipment
The rebroadcast systçm contains an outdoor receiving antenna, broadband amplifiers for the
standard AM and FM bands (530—1620 kllz and 88—108 mHz), a radiating tunnel antenna,
and an operator switching/microphone/VHS cassette recorder.
Two-Way Radio. This system will be used by tunnel staff in vehicles or with handhe]d
transceivers for communication between individuals. It is coordinated by the control center

18. operator. A dedicated VHF channel must be obtained for this two-way FM communication
system. Local police, fire, and medical assistance may also be included in the system.
Telephone. A direct dialing telephone system for communications within the portal building,
between cross- passages, and externally is provided by the EPAUX.
Motorist Call Boxes. The motorist call boxes provide direct communication with the contcol
center operator, who can organize assistance as required. The call boxes should be installed at
each cross-passage and on pedestals on the immediate approach road. They should be hands-
free speaker- microphones with a call button. The operator will receive an alarm tone coded
to indicate the location of the call box and
will then activate the unit.
Cellular Telep hone. Provision should be included in the tunnel for the installation of a 800-
MHz cellular telephone system. There is an increasing use of mobile telephones to alert
tunnel operators of conditions in the tunneL
l!4uipment Locations
The layout of the tunnel services can best be accomplished by using a modular arrangement
or spacing to unify power feeds, remote terminal units, and maintenance areas in the cross-
passage. Using a 100-m (300-ft) spacing, equipment can be installed cross-passage. This
matrix arrangement shown in Table 24-1 illustrates modular spacing and preferred mounting
locations in the tunnel cross section.
CONTROL (DENThR
The contml center is designed for the man—machine interface requirements, for without the
need for human intervention, the computers could happily mu alone in a dark room. Much of
the tunnel operation can run automatically using programmed schedules based on the time of
day and limiting levels for changes. It is only when there is an abnormality that the Operator
is needed.
The control center is therefore configured to first provide displays of operating status for all
equipment and then providé means to change operation status (see Figure 24-1 1).
There may be some need for manual controls and hard- wired connections to field equipment,
but the basic configuratiou and communication to remove equipment is deetronic code and
computer-aided.
Status Displays
Means should be available to status of monitor all display devices, sensing monitors, and
operating equipment, but not
Table 24-1. Tunnel Control Ariangement

19. Fig. 24-11. Control ceuten
all at one time or even continuously. The priority level of status addressing should be
arranged in the followitig order.
First Priority. Traffic incidents or major equipment events that require urgent operator
response include
• Traffic accidents

20. • Firefsmoke detection
• Power failure
• Dangerous levels of CC)
• Hydrocarbon spillage
• High water levels in sumps
Second Priority. This level includes condition alerts such as detection of a possible inciident,
equipment failure. or communication shutdown. These alanns require operator
acknowledgment and are then recorded. The computer simplifies recordkeepiOg both by one-
line printout of a hardcopy (paper) record and by logging in computer file storage.
Third Priority. Every change in traffic control and
equipment operation is logged for record purposes.
Control Procedures
Three means of control should be -available to the operator and tunnel stalL
Computer ControL The primary control system allows the operator to send commands to the
computer using the keyboard or a mouse and computer graphics to call up preprogrammed
traffic management plans, ventilation plans, etc. These plans will be conflict-proof and can be
run concurrently with each other, but not layered.
Manual ControL Using the computer terminal, manual switches, or both, the operator can
make individual changes to any device or piece of equipment. Changes made manually may
not be conflict-proof and may change again with the introduction of a command using
preprogrammed plans. Manual control is usually used for testing and maintenance.
Local Con froL At the remote location of the device or piece of equipment, control is
accomplished by using its local intelligent or manual control (PC or switches). Changes can
be made here in the event of a communication failure from the control center or for testing
and maintenance.
Map Display Panel
This floor-to-ceiling display is arranged in a semicircle to provide a panoramic view of the
status displays to the operator. Centered in the panel are three large color video terminals to
display computer graphic text, macro/micro line diagrams of device/equipment
configurations, and their operating status. The central or primary screen will usually show a
mmimap of the tunnel and approach roads with the current traffic control plan in place. The
two flanking screens are used for backup and concurrent status call-up as pages from the
status menu. Running just above or below are the TV monitors arranged in direction to traffic
flow (top right to left, bottom left to right). If there is room to spare on each end of the panel,
it is used as a special enunciating display.

21. CCTV Monitory. For short tunnels with a few CCIV cameras, the display panel will contain
one monitor for each camera. With a larger number of tunnel cameras, monitor sequencing is
recommended with 3—10 tunnel cameras coupled to each monitor in the map display panel.
The sequence should not be a rotation on individual monitors but a rolling sequence through
the tunnel. For example, with a 3:1 ratio of cameras to monitors, 1/3 of the tunnel would be
displayed moving through the tunnel. In this way a continuous section of the tunnel can be
shown. Two separate monitors, one on each end of the panel, are for the portal approach road
cameras. The first sequencing monitor can also be dedicated to the second outdoor camera.
Incident Viewing. Upon alert of an incident the tunnel section display can be centered on the
incident site to show conditions upstream and downstream. The operator can pull down to the
console monitor the camera showing the incident and return the panel monitors to tunnel
sequencing.
Control Console
The operator’s position will enable the viewing of the entire map display panel, two master
video display units
(VDUs) for CCTV displays, and computer dialogue, each built into the console. Arranged
around this operating position are switching panels and radio/telephone handsets. The console
is U-shaped to provide desk working areas.
Annunciating or Switching Panel
The type or need for annunciating or switching panels depends on code or operating practice
particular to the location of the tunnel. A fire annunciating panel may be required here and at
the tunnel portals to conform with local regulations. The panel may also contain secondary or
backup manual switches for some or all of the tunnel equipment.
Supen4sor or Dispatch Desk
A second controllsupervisorfcominunication desk can be located in the control center or at a
secondary or remote location. The use of computer control and digital communication allows
this operating freedom. For large facilities with one or more tunnels, bridges, toll, or
maintenance facilities to manage, the communication needs will require this second desk.
With dual VDUs, switching, and communication devices, this subcenter can provide parallel
and backup control with the prime center subject to operations protocol.
Computers and Peripherals
The system is built around two industrial-grade minicomputers or PCs to provide 100%
redundancy (see Figure
• 24-12). Each computer (CPU) is sized and equipped with dual disk drives, clocks, a
watchdog unit, and a cotnmunicalions unit, so that individually each CPU can support all
operationlalertfrecording requirements. Both CPUs are supplied with operating programs, but
they are not expected to perform parallel processing. The operating software is configured to

22. allow the backup to assume command by simply polling status of displays and operating
levels. Included in the computer room is a program desk with a terminal and keyboard to be
used for testing and maintenance. This station, as with all computer input terminals, should
be tied
Fig. 24-12. Cennal control layout.
into access passwords to protect access and use of the computer systems.
Communication Network
The most expensive element of the control system is the communication network. Cost and
limitations of a hard-wired system have led to the use of single cable for multiplexing data
transmission. flpical single cables of twisted-pair, coaxial and/or fiber optic are now used
with time-division (1DM) and/or frequency-division (FDM) multiplexing.
Advances in the use of programmable controllers (PECs) has also relieved the data
processing load in the control center CPUs and the volume of data interchanged between field
units and the control center. This concept of distributed intelligence with multiplexing
transmissions is the basis of a supervisory control and data acquisition (SCADA) system (see
Figure 24-13).
SCADA Configuration
The communication system is made reliable by usingtwo techniques. The first technique is
distributed processing, which involves the spreading of control processing throughout she
network to minimize the severity of a single failure. Coupled with this is network
redundancy. If the primary route of communication has failed, then communication s
transferred to a secondary route- In simple tenns, the control center is usually in a state of
waiting, receivingdevice and equipment status reports from remote terminal units (RTIJs).
When called into action, they send execution commands to the RTUs and then verify that the
proper change has been carried out. The RTUs control. the various downline 4evices and
equipment, which include

23. FIg. 24-13. Network.
1. Traffic detectors sending data back to the control center
2. Traffic control equipment on hold waiting for commands, which send basic status to the
control center to confirm availability
Distributed Intelligence
The control center will have the capability to interrupt and when necessary take over the
duties of any downline R1’U using reserve capacity built into the communications network.
Depending on the size and number of RTUs, there may be a need for two levels of downline
data processing. An example of this would be a local master RTU controlling
severalsubsystems that have RTUs at each piece of equipment. One or more of these master
RTUs would feed information and receive commands fron the control center, and supervise
the RTIJs to create a self-contained operating unit. These master RTIJs can assume command
in the event of a communications break from control center.
Cable Network
The communication cable network should be configured on a semi- or, preferably, fully
duplex loop to transmit and receive data simultaneously. Should a break occur within the
loop, it will automatically switch to semiduplex operation. The use of independent
communication loops can allow the grouping of devices and equipment having similar
priority and need for high-speed transmission rate and data refreshment Other pieces may
only need periodic contact at slow speeds and can be grouped on separate cabling loops.
Codes of practice may also require separate cabling as for fire detection or alarms.
Software

24. Recent developments of computer control for industrial applications have made real-time
multitasking systems available in several software packages that can be used for the general-
purpose software. By using these general application packages, the amount of purpose-
written software is reduced and made easier to prepare. The tunnel system package loaded
into the central computers and downline in the programmable controllers should meet the
following requirements.
Input/Output (110). Measurements from field monitors and change commands form this link.
This data is usually translated to digital code. The 1/0 processing speed of this data is critical
and must be optimized to handle the number of I/Os to be scanned while maintaining an
acceptable level of responsiveness.
Man—Machine Interface (MMI). The preferred interface is computer graphics with
simulated network, control panels. and logic diagrams for visual displays. Data may be input
via keyboard commands, although using a mouse or trackball to manipulate a graphical user
interface is more common. Programmed sequencing of group commands is essential for
critical action, particularly when a trained operator
is not available. Using these devices, the operator should be able to window in quickly for
status, operating, or diagnostic plans that give an overview or point display of all systems.
Sound alarms including voice simulation are gaining use for MMI and are recommended.
Operating Plans and Algorithms. Within the software will be routines ranging from complex
data manipulation at the central computer to relay-ladder-logic at the PLCs. These operating
plans and modifications of parameter are resident in the system’s operating plans.
Database. The organization setup is housed here to assign locations, sequencing, alarms,
timing, and reporting for all functional subroutines. Included are historical backgrounds of
actual operating experience for input into the operating plan.
Communications Network. The SCADA network should conform to an industry standard for
a local area network (LAN).
t’urpose-Wxitten Software
Title headings for tasks to be included in the application
software are
• Monitoring. Incident detection, CO levels, visibility, heat and smoke detection, sump water
levels, power and equipment failures
• Man-machine interface. Computer gtaphics, alarm priority
• Operating plans. Traffic control, emergency response management, ventilation control,
plant management

25. • Security. Entry surveillance, computer usage, watchdog, emergency power, system
shutdown
• Recordkeepihg. Event logs, operating timing, traffic and ventilation histograms
• Maintenance. Operating logs, servicing alarms
• Training. Operation simulation
SYSTEM SEIJECUON
There are concerns for cost cutting and the question of whether certain features are really
necessary. The basic system requirements for a short tunnel in the country and an urban high-
volume tunnel are very much the same: attention to tunnel user needs. An answer to the cost
question is non- quantifiable, but how well a tunnel performs is its most visible feature. Since
there is such a large investment in building a tunnel, why compromise with its operational
capabilities?
Basic Requirements
The basic components that should be included in the surveilmance and control system are
Traffic service. A full-time means toidentify stopped or disabled vehicles in the tunnel, their
verification, and availability of on-call emergency response
• Fire service. A proven means to identify or detect fire or smoke, and the means to fight fires
and evacuate trapped motorists in the tunnel
• Environment. Continual monitoring of levels of tunnel pollution and a means to dilute
excessive amounts
• Lighting. Full-time tunnel illumination with battery backup to prevent total darkness
Flooding. A drainage system including sumps. pumps, and
outfalls/storage -
• Power. Dual sources of power supply or a built-ia standby diesel electric power unit
DESIGN AN!) IMPLEMENTATION
System design employs engineering techniques from traffic engineering,
computer/communication design, and software development. To produce a successful end
product, their combined input is required from design inception to final acceptance testing
and hand over to a client.
Traditional Design
Thete are two basic design and contracting methods used to implement the system—the
traditional preparation of design plans and specifications for contractor construction, or the

26. system manager approach. For the former, the designer prepares either a materials/installation
specification or a per
-formance specification for typical contract bidding to furnish/install or
design/purchase/install. This method can be successful only by contracting directly with
prequalified control system contractors. When this specialty work -is lost within a large
tunnel civil contract, it is difficult to stop this element from being slighted by the prime
contractor and viewed as a nuisance to be passd piecemeal to subcontractors. Success is
seldom certain.
System Manager
The system manager is -a selected firm working under an engineering service contract to
design, prepare procuremeat and installation contracts, and be responsible for system
integration, documentation, and training. Underthis method there is freedom to make changes
as the system is being developed without the responsibility of claims for extras. The system
manager provides the application software, which is the key element-in a successful
operating system. -
The complete services package associated with a control system should include the
following:
Operating manuaL The design and installation reflect specific operating procedures to define
goals that should be spelled out in this manuaL This document should be flrstorganized in the
system inception stage and then refmed -and updated throughout the design and installation
process.
- Maintenance manuaL This is an organized reference of original designs, shop drawings,
manufacturers’ pedifrcations, and maintenance procedures with parts listed for all hardware
items. The software manual should include descriptions of source programs and
programming instructions for diagnostics and parameter changing.
Training. Formal book and classroom training may familiarize staff with the system, but the
opportunity for hands-on involvement with the contractor/system manager during installation,
testing, and commissions is far superior.
Initial operatioa Provisions to supply a management staff during start-up for a specified
period to further train the takeover staff, debug the software, and apply corrective
inaintenánce is a sound investment It also gives greater assurance that the warranty/guarantee
response will be prompt and complete.
Warranty/guarantee. This provision ensures responsibility for a specified period for all
components including nnnufacturer product in-house warranties that may have expired
OPERATION AND MAINTENANCE

27. There are two types of tunnel facilities: tunnels with tolling and those without. The former
tend to become kingdoms unto themselves, while the later will contain essential staff and
equipment and thus better illustrate the basic needs for operating and maintaining a tunnel.
Organization
The tunnel organization is made up of day staff working a regular 8-hour day, 5 days a week,
and shift workers assigned to the day shift from 6 A.M. to 2 P.M., a night shift- from 2P.M.
to 10 P.M. or the graveyard shift from 10 P.M. to 6 A.M., on a ‘7 days a week operation. The
number of employees needed to man the shifts will be 40% more than the actual number to
cover a 7-day week, holidays, vacations, etc. The thy staff perform routine administrative and
maintenance tasks. The shift workers monitor traffic, inspect and perform routine
maintenance, and are on call for êmergencies. During the graveyard shift, most of the major
maintenance work is carried out. The permanent tunnel staff supervise temporary or
contracted laborers and specialists.
Permanent Key Staff
The permanent key staff is divided into three divisions having the following duties (see Table
24-2):
Management.
• Tunnel manager Provides overall facility management, maintains dealings with government
agencies, the community and contracted services.
• Supervisors. One supervisor is assigned to each of the three shifts to supervise the day-to-
day operation and management of the tunnel, working staff, and contracted services.
Assumes command for emergency response.
• Administration. An administrator, secretary, and clerk handle correspondence, budget,
finances, and purchasing.
Table 24-2. Permanent Key Staff
Operations.
• Control center operators. The center is manned continually with an operator who monitors
traffic and equipment operation. The shift supervisor provides his relief

28. • Response crew. This crew is manned by two members on both the day and night shift and
one for the graveyard shift. They are the manual arm for the control center operator to man
the emergency response wreckers, check prohibited vehicles, assist motorists, enforce traffic
control, and keep the roadways clear.
Maintenance.
• Technical specialists. This four-member crew, three on day shift and one on graveyard shift,
perform routine inspection and equipment maintenance and supervise contracted services
work. Included in this crew are technical specialists in mechanical, electrical, and electronic
equipment.
• Maintenance crew. Included with the shift workers is a labor force to assist the technical
specialists to perform general janitorial, cleanup, painting, patching, replacement, and repair
work. This crew can be permanent staff, part-time drawn from a larger Highway Department,
or included in contracted services (i.e., janitorial, tunnel washing).
Contracted Services. Many large transportation authorities serving a number of facilities
including tunnels have their own workshops, staff, and equipment to be almost 100% self-
maintaining. However, for most individual tunnels it has been found beneficial to contract out
all maintenance work except for the day-to-day caittaking. Included below are the
professional and technical services suitable for on-call and off-site service:
• ProfessionaL L.egal, labor relation, employment service, engineering, facility inspection,
accounting
• Site maintenance. Structural repairs, paving, lighting, lamp replacing, signing, pavement
marking, painting, tunnel washing, janitorial
• Equipment repair Fan motors, pumps switchgear, electronic equipment
• Equipment servicing. Computers, radios, telephones, data transmission, office equipment
Tolling Facilities. There are few tunnel facilities where tolls are not needed: no tolls, no
tunnel. For tunnel operation, a toll plaza is a godsend where oversize or hazardous
cargo vehicles are easily dealt with. It provides a built-in traffic crossover or turn—back area
and can be the excuse for traffic delays.
Toll Plaza Layout. The usual transition and number of toil booths in the plaza are three
booths per throughroadway traffic lane arranged with a truck lane(s). The booth should be
arranged to gap automatic collection with manual collecdon. There is a strong move to
introduce automatic vehicle identification (AVI) for toll collection.
Plaza Locaáon. The tolling facility may be located immediately in front of the tunnel portal to
consolidate tunnel operations and tolling.

29. • Toll supervisor Stationed in the support building (administration or toll building) with an
overview of the plaza operation; the supervisor maintains supervision of toll plaza operations.
• Toll collectors. Shift workers in the collection booths to handle manual and truck booths. A
plaza supervisor is included to oversee operations and provide relief.
• Revenue security. The collection of manual and automatic collection bàoths revenue is
bandied by this group together with the assembly of change packages and the accounEing of
return packages. Coin and token counting is also handled by this group.